1. Field of the Invention
The present invention relates to continuously variable transmissions. More specifically, the present invention relates to dual drive continuously variable transmissions having dual drives slaved together for transfer of torque from input shafts to output shafts.
2. Description of the Related Art
Continuously variable transmissions (“CVTs”) are a type of transmission capable of transferring torque from an input shaft to an output shaft. The CVT is a transmission that is capable of converting input speeds into output speeds that are steplessly variable within a given range. Recently, the automotive industry has used these transmissions for transferring torque between an input shaft and an output shaft of a vehicle employing a low horsepower engine.
The most common of such CVT drives for automobiles has used a steel segmented V-belt operating with axially moveable steel pulleys that force belt radial movement along the conical pulley surfaces to change the speed ratio between the driven and the output shaft, usually by a combination of springs and hydraulic generated force. Such belts operate the drive by transferring the torque from an input shaft, through a single input pulley, to a single output pulley and, ultimately, to an output shaft. Drives of this type have been successful and, as mentioned above, are currently being commercially produced in the lower horsepower range of passenger automobiles.
Operational qualities of CVT drives are well known in the automotive industry, including their shortcomings. Continuous research and development effort is being expended in the automobile industry to extend the capabilities of the belt and pulley basic concept because of the perceived advantages to be realized over more traditional transmissions now in production.